Paint substitute film and method of applying same

ABSTRACT

A paint substitute film product  1  for surfacing an object S includes a decorative coat including a light-curable resinous layer, and a protective film provided over a surface of the light-curable resinous layer of the decorative coat. An adhesion strength AS1 between a surface of the object and the decorative coat, an adhesion strength AS2 between the protective film and the decorative coat, and a tensile strength TS of the decorative coat are configured to exhibit the equation: AS1&gt;AS2&gt;TS. The paint substitute film product  1  can deliver increased economy in surfacing the object, and the step of forming the object to be surfaced and the step of applying the paint substitute film can be provided independently.

BACKGROUND OF THE INVENTION

[0001] This invention relates to a paint substitute film used assubstitutes for painting of exterior components of an automobile or thelike.

[0002] In order to improve an ornamental design of exterior componentsor trims, such as fenders, bumpers, hoods, wheel caps, and other plasticcomponents, of a vehicle, spray paint is employed in most instances.However, a painting process including an operation of spraying paintrequires a large facility and wide space for repeatedly performedpainting and drying steps and thus would disadvantageously reduceproductivity and manageability. In this respect, an alternative approachhas been sought, and an application of a colored decorative film(hereinafter referred to as “paint substitute film”) to an exteriorcomponent or the like as substitutes for the painting process has beenreceiving attention in recent years.

[0003] A paint substitute film as conventionally used, for example asdisclosed in JP 63-123469 A, has a trilaminar structure including atransparent layer, a pigmented coating, and an adhesive layer. JP63-123469 A teaches a process of applying the film to a target object towhich a decorative effect will be given. The process is schematicallyillustrated in FIGS. 6A-6D. First, as shown in FIG. 6A, the film 31 isformed three-dimensionally in a supporting mold 32 so as to conform to acontoured surface of the target object; then, as shown in FIG. 6B, endportions of the film 31 are trimmed off. The trimmed film 31 is placedfor example into an injection mold 34 as shown in FIG. 6C, and bonded tothe target object 33 while the target object 33 is being formed. Aresultant casting of a decorated component is taken out of the injectionmold 34 as shown in FIG. 6D. Another technique for applying a paintsubstitute film using an injection mold is disclosed in JP 7-9484 A.

[0004] The process of applying a paint substitute film as illustrated inFIGS. 6A-6D require a trimming step using a cutting blade, a laser, ahot wire or the like. In particular, when the target object 33 to whicha decorative effect will be given has a complicate shape, a trimmedportion thereof becomes complicate too, and thus the cost incurred forthe trimming step would add up, which could eventually raise the totalcost of production, thereby making the final casting expensive.

[0005] In addition, with the above-described technique using theinjection molding, molding of the target object and applying of thepaint substitute film are performed simultaneously in the same processstep; therefore, the applicable target object (component) shoulddisadvantageously be restricted to those made of materials which can beformed by injection molding.

[0006] The present invention has been created to address theabove-discussed disadvantages.

SUMMARY OF THE INVENTION

[0007] In one aspect of the present invention, there is provided a paintsubstitute film product for surfacing an object, comprising a decorativecoat including a light-curable resinous layer, and a protective filmprovided over a surface of the light-curable resinous layer of thedecorative coat, wherein the following equation is satisfied:

AS1>AS2>TS  (1)

[0008] where AS1 denotes an adhesion strength between the surface of theobject and the decorative coat, AS2 denotes an adhesion strength betweenthe protective film and the decorative coat, and TS denotes a tensilestrength of the decorative coat.

[0009] Since Equation (1) is satisfied, the paint substitute filmproduct can be trimmed of an excess end portion thereof automaticallywhile the protective film is peeled off; i.e., the protective film andthe excess end portion of the paint substitute film product are removedfrom the decorative film adhered to the surface of the objectsimultaneously in one and the same operation. Accordingly, the step oftrimming as a separate process step is not necessitated. In thisrespect, the above paint substitute film product can deliver increasedeconomy in surfacing the object. Moreover, the paint substitute film(decorative coat) can be applied to any objects provided off the shelf;in other words, the material of the target object to which a desireddecorative effect is to be given is not limited to the materials fit forsubjecting to injection molding.

[0010] The above paint substitute film product may preferably beconfigured such that the light-curable resinous layer that has beencured exhibits an elongation percentage ranging between 5% and 10%inclusive. This configuration provides good conformity to a variety ofdegrees of convexity in the shapes of the objects to be surfaced, andserves to make the trimmed end face of the decorative coat smooth.

[0011] In another aspect of the present invention, there is provided amethod of applying a paint substitute film to a surface of an object.The method includes the steps of: (1) adhering the above paintsubstitute film product to the surface of the object so that an end ofthe paint substitute film product overreaches an boundary of the surfaceof the object, to form an excess end portion of the paint substitutefilm product; (2) irradiating the light-curable resinous layer withlight through the protective film to cure the light-curable resinouslayer; (3) peeling off the protective film from the decorative coatwhile removing the excess end portion from the paint substitute filmproduct adhered to the surface of the object.

[0012] The above method can serve to obviate the need for a separatestep of trimming, and thus deliver increased economy in surfacing theobject. Moreover, the paint substitute film (decorative coat of thepaint substitute film product) can be applied to any objects providedoff the shelf; in other words, the material of the target object towhich a desired decorative effect is to be given is not limited to thematerials suitable for injection molding. Further, the above methodprovides a simplified process, which serves to improve productionefficiency of the desirably surfaced castings.

[0013] Other advantages and further features of the present inventionwill become readily apparent from the following description of preferredembodiments with reference to accompanying drawings.

BRIEF DESCRIPTION OF THE DRAWINGS

[0014]FIG. 1 is a partial magnified view in cross section of a paintsubstitute film product according to the present invention.

[0015]FIG. 2 is a schematic diagram for explaining an application of thepaint substitute film product to an object to be surfaced with a paintsubstitute film.

[0016]FIGS. 3A through 3B are schematic views in cross section of apaint substitute film product applied to an object to be surfaced forexplaining features and operations thereof. FIG. 3A shows a state of thepaint substitute film product with a protective film remaining on adecorative coat thereof; FIG. 3B shows a state of the paint substitutefilm product of which the protective film is being peeled off; and FIG.3C shows a state of the paint substitute film product from which theprotective film and excess end portion thereof are removed.

[0017]FIG. 4 is a schematic diagram for illustrating a tensile test forthe decorative coat.

[0018]FIG. 5 is a schematic diagram for illustrating a shear adhesiontest for verifying adhesion strength between the decorative coat and theprotective film.

[0019]FIG. 6 is a schematic diagram for illustrating a process ofapplying a conventional paint substitute film to an object to besurfaced therewith.

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

[0020] A description will be given of preferred embodiments of thepresent invention with reference to the drawings. As shown in FIG. 1, apaint substitute film product 1 includes from outside (front side)thereof a protective film 2 and a decorative coat 3. The decorative coat3 includes a light-curable resinous layer 4 formed at a location nearthe protective film 2. The decorative coat 3 has a trilaminar structureincluding from outside (front side) thereof the light-curable resinouslayer 4, a color coat 5 and an adhesive layer 6. In the presentembodiment, the light-curable resinous layer 4 is in contact with theprotective film 2, but the location of the light-curable resinous layer4 according to the present invention is not limited thereto. In otherwords, the light-curable resinous layer 4 is provided between theprotective film 2 and the color coat 5, and the protective film 2 isprovided over a surface of the light-curable resinous layer for exampleto protect the decorative coat 3 (i.e., the color coat 5 thereof) untilthe paint substitute film (decorative coat 3) is adhered to an object Sto be surfaced (see FIG. 2) (i.e., before the light-curable resinouslayer 4 is cured). The protective film 2 is an element to be peeled offafter the paint substitute film is adhered to the object S to besurfaced (and the light curable resinous layer 4 is cured).

[0021] Considerations to be given in the choice of materials of theprotective film 2 are as follows:

[0022] (1) high solvent resistance; that is, capability of preventingcracks that would otherwise occur due to solvent included inlight-curable resins applied to the protective film 2 when thelight-curable resinous layer 4 is formed;

[0023] (2) high transparency; that is, capability of transmitting lightsuch that the light-curable resinous layer 4 can be cured by the lightpassing through the protective film 2;

[0024] (3) sufficient elongation percentage; that is, elongationproperty that permits the protective film 2 to conform to the shape ofthe object S to be surfaced, even if the object S to be surfaced has aconvexly curved portion as shown in FIG. 2 or deep-drawn portion; and

[0025] (4) appropriate peeling ease; that is, the protective film 2 canbe peeled off as necessary.

[0026] Films having the above preferable features for the protectivefilm 2, for example, include a non-oriented polyethylene terephthaletefilm and a non-oriented polypropylene film. The thickness of theprotective film 2 may preferably fall within a range of 50 μm through300 μm, because too thin film would impair handleability and too thickfilm would reduce formability. In particular instances, a laminate ofthe non-oriented polyethylene terephthalete film and the non-orientedpolypropylene film, or the like may be employed for the protective film2.

[0027] The light-curable resinous layer 4 may for example include amixture of an acrylic polymer, a urethane oligomer, an elastomercomponent and a photopolymerization initiator. This mixture initiatesconsecutive polymerization on exposure to ultraviolet radiation, to forman acryl-based resinous coat. Since the light-curable resinous layer 4becomes the outmost surface of the paint substitute film after theprotective film 2 is removed, the light-curable resinous layer 4, whencured, may preferably have sufficiently high wear and chemicalresistance. In this respect, the aforementioned resin is one of thedesirable materials. The light-curable resinous layer 4 havingsufficiently high wear and chemical resistance after it is cured cansave the need for having another protective coat formed thereon, and canthus provide a cost-effective paint substitute film product 1.

[0028] Moreover, the light-curable resinous layer 4 may preferably beconfigured to, when cured, exhibit an elongation percentage rangingbetween 5% and 10% inclusive, where the elongation percentage is apercentage of elongation until fracture occurs (maximum elongationpercentage at break) using a tensile test for a decorative coat 3 with atest specimen of 25 mm in width, at a tension speed of 50 mm/min. in alongitudinal direction, as shown in FIG. 4. The reasons therefor will begiven later.

[0029] The color coat 5 is a layer having a colored portion serving as asubstitute for painting, which may for example be made of a colormaterial including pigments or dyes as prepared in a desired color and apolyurethane resin as a binder. Adhesive agents for forming the adhesivelayer 6 may be selected as appropriate in accordance with the materialof an object S to be surfaced, for example from organic materialscontaining an epoxy group or an urethane group.

[0030] The paint substitute film product 1 having a layered structure asdescribed above may be fabricated without any particular limitationplaced on its method or apparatus. For example, a coating apparatusknown in the art such as a roll coater, a knife coater and a commacoater may be used to apply resins for the light-curable resinous layer4, color coat 5, and adhesive layer 6 in this order to the protectivefilm 2.

[0031] This is one of economical methods for fabricating the paintsubstitute film product 1. In one aspect, the present invention ischaracterized by a particular relationship among an adhesion strengthAS1 between a surface of the object S to be surfaced and the decorativecoat 3 (i.e., the adhesive layer 6 thereof), an adhesion strength A2between the protective film 2 and the decorative coat 3 (i.e., thelight-curable resinous layer 4 thereof) and a tensile strength TS of thedecorative coat 3, which relationship is given by Equation (1) below:

AS1>AS2>TS  (1)

[0032] where the tensile strength TS is a stress required to entirelyrupture the decorative coat 3 when a stretching load given to thedecorative coat 3 in a direction parallel to a surface thereof. Theunits for use with the strength AS1, AS2 and TS are strength per unitarea.

[0033] The inventors verified the relationship between the adhesionstrength AS1 and AS2 through a shear adhesion test carried out with ashearing direction of the paint substitute film product 1 being parallelto the surface of the paint substitute film product 1, as shown in FIG.5. The shear adhesion test uses a test specimen of 25 mm in width and 25mm in overlap length in the shearing direction between the protectivefilm 2 and the object S to be surfaced, and the protective film 2 ispulled at a tension speed of 50 mm/min. The inventors verified thetensile strength TS through a tensile test (decorative coat tensilestrength test) as described above with reference to FIG. 4.

[0034] The results of the tests as described above have shown that thetensile strength TS stands at 19.6 KPa and the adhesion strength AS2stands at 118 KPa. None of peel, break, shear, wrinkling or the like hasbeen observed between the object S to be surfaced and the decorativecoat 3, and it has thus turned out that the adhesion strength AS1 has anadhesion strength greater than 118 KPa at the least. From the foregoing,it has been verified that the paint substitute film product 1 has afeature exhibiting a relationship given by Equation (1).

[0035] It has also been verified that the thickness of the decorativecoat 3 in its entirety may be adjusted to 100 μm or thinner in order toobtain a favorable property for establishing a relationship of AS2>TS.The adhesion strength AS2 between the protective film 2 and thedecorative coat 3 (i.e., light-curable resinous layer 4) is a strengthderived mainly from vacuum adhesion of a contact surface therebetween,and it would thus be relatively difficult to adjust the value of theadhesion strength AS2. Therefore, in an effort to make it easier toobtain a favorable property for establishing the relationship of AS2>TS,it has turned out that the tensile strength TS may be adjusted correctlywithout substantial variation among products by making the thickness ofthe decorative coat 3 equal to or thinner than 100 μm in its entirety.

[0036] Hereafter, a description will be given of a process of applying apaint substitute film to an object S to be surfaced. The object S to besurfaced may include, but not be limited to, exterior components such asa bumper, etc.

[0037] First of all, the paint substitute film product 1 is adhered to asurface of the object S for example by vacuum forming or the like. Inparticular, a double-sided suction vacuum forming device (not shown)known in the art may be employed to obtain a desired product withoutmarks of suction holes left on the decorated surface of the object S.Accordingly, the paint substitute film product 1 is adhered to theobject S to be surfaced with an adhesion strength AS1 as describedabove. Hereupon, the paint substitute film product 1 is adhered to theobject S so that an end of the paint substitute film product 1overreaches a boundary of the surface of the object S, to form an excessend portion 1 a, which is not adhered to the object S, of the paintsubstitute film product 1.

[0038] Next, ultraviolet light is radiated through the protective film 2to cure the light-curable resinous layer 4. When the light-curableresinous layer 4 is cured, the protective film 2 is peeled off as shownin FIG. 3B from the decorative coat 3. Since the relationship of AS1>AS2is being established, the decorative coat 3 remains adhered to theobject S to be surfaced, while the protective film 2 alone is peeledoff. Moreover, the decorative coat 3 is being adhered with the adhesionstrength AS1, and thus a portion thereof adhered to the object S wouldnever be ruptured when the protective film 2 is peeled off.

[0039] The protective film 2 that has been peeled off up to the end ofthe object S is then removed together with the excess end portion 1 aruptured off at the end of the object S from the paint substitute film.The excess end portion 1 a is ruptured off at the end of the object Sbecause no adhesion strength AS1 acts on the excess end portion 1 awhile the adhesion strength AS2 acting on the excess end portion 1 a isgreater than the tensile strength TS thereof. Consequently, the paintsubstitute film can be trimmed automatically of the end portion when theprotective film 2 is peeled off, and thus the final casting with adesired decorative effect can be obtained without an extra process stepof trimming off the excess end portion 1 a of the paint substitute filmproduct 1.

[0040] The elongation percentage the light-curable resinous layer 4 thatcan exhibit after it is cured may preferably range between 5% and 10%inclusive for reasons as cited below. If the elongation percentage isless than 5%, the light-curable resinous layer 4 cannot conform to thechange in shape (swelling or shrinking with temperature change, or thelike) of the object S to be surfaced when the paint substitute film isapplied to the object S, so that a fracture in the film would be likelyto occur. If the elongation percentage is more than 10%, the decorativecoat 3 would be likely to undergo elongation when the protective film 2is peeled off, with the result that removing the excess end portion 1 awould leave burrs or ragged edges in a fracture surface of the paintsubstitute film, and thus a smoothly trimmed surface could not beobtained. To prevent such problems, the light-curable resinous layer isconfigured to, when cured, exhibit an elongation percentage rangingbetween 5% and 10% inclusive to fabricate a desirable paint substitutefilm product 1.

[0041] Although the preferred embodiments of the present invention havebeen described above, layouts, shapes, and so forth of the elements arenot limited to those illustrated in the drawings, and variousmodifications and changes may be made in the present invention withoutdeparting from the spirit and scope thereof. In the above description ofthe preferred embodiment of the present invention, it is assumed thatthe paint substitute film is applied to a component of an automobile orthe like. However, the object S to be surfaced according to the presentinvention is not limited thereto, but the paint substitute film can beapplied to vehicles other than an automobile (e.g., motorcycles, trucks,etc.), vessels (e.g., ships, motorboats, etc.), home electricalappliances, audio products, construction materials, steel sheet or plateproducts, and the like.

[0042] In conclusion, according to the present invention, the adhesionstrength AS1 between the surface of the object and the decorative coat,the adhesion strength AS2 between the protective film and the decorativecoat, and the tensile strength TS of the decorative coat represent therelationship as given by Equation (1):

AS1>AS2>TS  (1)

[0043] Since Equation (1) is satisfied, the paint substitute filmproduct can be trimmed of an excess end portion thereof automaticallywhile the protective film is peeled off; i.e., the protective film andthe excess end portion of the paint substitute film product are removedfrom the decorative film adhered to the surface of the objectsimultaneously in one and the same operation. Accordingly, the step oftrimming as a separate process step is not necessitated. Therefore, theabove paint substitute film product can deliver increased economy insurfacing the object. Moreover, the paint substitute film (decorativecoat) can be applied to any objects provided off the shelf; in otherwords, the material of the target object to which a desired decorativeeffect is to be given is not limited to the materials fit for subjectingto injection molding. Further, the step of forming the object to besurfaced and the step of applying the paint substitute film can beprovided independently.

What is claimed is:
 1. A paint substitute film product for surfacing anobject, comprising: a decorative coat including a light-curable resinouslayer; and a protective film provided over a surface of thelight-curable resinous layer of the decorative coat, wherein thefollowing equation is satisfied: AS1>AS2>TS where AS1 denotes anadhesion strength between a surface of the object and the decorativecoat, AS2 denotes an adhesion strength between the protective film andthe decorative coat, and TS denotes a tensile strength of the decorativecoat.
 2. A paint substitute film product according to claim 1 whereinthe light-curable resinous layer, when cured, exhibits an elongationpercentage ranging between 5% and 10% inclusive.
 3. A paint substitutefilm product according to claim 1 wherein the protective film is formedof a material selected from the group consisting of non-orientedpolyethylene terephthalete film, non-oriented polypropylene film, and alaminate of the non-oriented polyethylene terephthalete film and thenon-oriented polypropylene film.
 4. A paint substitute film productaccording to claim 1 wherein the protective film is formed with athickness ranging between 50 μm and 300 μm inclusive.
 5. A paintsubstitute film product according to claim 1, wherein the light-curableresinous layer includes a mixture of an acrylic polymer, a urethaneoligomer, an elastomer component and a photopolymerization initiator. 6.A paint substitute film product according to claim 1, wherein thedecorative coat is formed with a thickness of 100 μm or thinner.
 7. Amethod of applying a paint substitute film to a surface of an object,the method comprising the steps of: (1) adhering a paint substitute filmproduct according to claim 1 to the surface of the object so that an endof the paint substitute film product overreaches an boundary of thesurface of the object, to form an excess end portion of the paintsubstitute film product; (2) irradiating the light-curable resinouslayer with light through the protective film to cure the light-curableresinous layer; and (3) peeling off the protective film from thedecorative coat while removing the excess end portion from the paintsubstitute film product adhered to the surface of the object.